The benzazepinones produced by the method of the present invention are compounds of seven-membered lactam rings fused to benzene rings. In contrast with five- or six-membered rings fused to benzene rings, the formation of which is often reported and is comparatively readily attained, such seven-membered rings found in benzazepinones are very difficult to form, and methods using carbon-carbon bond formation within aromatic rings need specific substrates or harsh reaction conditions.
For example, as methods for synthesizing benzazepinones, methods in which 1-aminoazepin-2-one derivatives are synthesized through intramolecular cyclization reaction of bis(methoxycarbonylamino)acetic acid derivatives (see Non-patent Document 1, for example) are known. However, such methods require special and expensive bis(alkoxycarbonylamino)acetic acid, and thus are not appropriate methods in terms of industry. Moreover, a method in which sulfuric acid and a phenylacetylamide derivative having dimethylacetal are treated at high temperature to form an azepinone ring through intramolecular cyclization reaction, followed by oxidation of the 1-position and a method in which aluminum chloride and 2-chloro-N-phenethyl-N-methylacetamide are treated at high temperature to form an azepinone ring through intramolecular Friedel-Crafts reaction, followed by oxidation of the 1-position (see Patent Document 1, for example) are also known. However, all of these methods need harsh conditions at excessively high temperatures with highly reactive reagents, and thus are considered to be difficult to control in terms of industry. Moreover, the 1-position has to be oxidized after the cyclization, and therefore these methods can hardly be efficient.
Furthermore, as a method for synthesizing benzazepinones under relatively mild conditions, a method which use cyclization reaction of Pummerer type rearrangement with sulfoxides is reported (see Non-patent Document 2, for example). However, this method requires many steps for introducing and removing sulfoxides and uses expensive periodates, and thus can hardly be appropriate methods in terms of industry.
On the other hand, a method in which an azepinone ring is formed through amide bond formation, is also reported. However, expensive reagents are required for a method in which an azepinone ring is formed after forming a biaryl compound through Suzuki coupling reaction (see Non-patent Document 3, for example). Moreover, a method in which an azepinone ring is formed after carboxylation (see Patent Document 2, for example) is also known. However, this method requires cryogenic reaction using a strong base for the carboxylation, and thus can not be inexpensive industrial production methods. Moreover, all cases are limited to dibenz[b,d]azepin-2-one skeletons, and the 1-position has to be oxidized. Therefore, these methods are not versatile and inefficient.    Patent Document 1: PCT International Publication No. WO 2002/47671    Patent Document 2 PCT International Publication No. WO 1999/66934    Non-patent Document 1: Tetrahedron, 1987, 43, 439.    Non-patent Document 2: Chem. Pharm. Bull., 1989, 37, 939.    Non-patent Document 3: J. Org. Chem., 2002, 67, 1199.